THE PICM-19 CELL LINE AS AN IN VITRO MODEL OF LIVER BILE DUCTULES.

Authors: Talbot, Neil; Caperna, Thomas; Wells, Kevin

Submitted to: Journal of Cells Tissues and Organs
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/11/2001
Publication Date: 1/1/2002
Citation: Talbot, N.C., Caperna, T.J., Wells, K.D. The picm-19 cell line as an in vitro model of liver bile ductules. Journal of Cells Tissues and Organs. 171:99-116. 2002.

Interpretive Summary: The PICM-19 fetal liver cell line was isolated from the primary culture and spontaneous differentiation of pig epiblast cells, i.e., from pig embryonic stem cells. Besides this unique origin, the PICM-19 cells are also unique in displaying an ability to become either bile duct-like cells or hepatocyte-like cells; the two cell types that perform the vital functions of the liver. This report demonstrates another unique feature of the cell line. That is, the ability to direct the cells to form bile ducts by changing the pH of the culture medium from 7.3, the normal pH of the body, to pH 7.8. The report goes on to demonstrate the utility of the PICM-19 cells as an in vitro model of bile duct tissue. It is shown that the PICM-19 cells ductal structures can be stimulated or inhibited by molecules that normally stimulate or inhibit bile duct function in the intact liver. The stimulation or inhibition responses of the PICM-19 cells are similar in ndose and speed to that found in the body. The PICM-19 cell line is therefore a good model of bile duct epithelium and is unique in being the only cell line of any species that actually forms functional bile ductules in vitro, i.e., out of the body. Therefore, the PICM-19 cell line should be useful to researchers wishing to study bile duct function and pathology, and it should also be useful for toxicological studies as an alternative to animal testing.

Technical Abstract: The PICM-19 fetal liver cell line was isolated from the primary culture and spontaneous differentiation of pig epiblast cells, i.e., embryonic stem cells. PICM-19 cells were induced to differentiate into ductular formations by culturing at elevated pH, and the ductules were functionally assayed to establish their usefulness as an in vitro model of bile duct epithelium. The in vitro produced ductal structures were exposed to cAMP inducing agents and bioactive peptides reported to influence the secretory activity of liver bile ductules. The secretory response of the cells was assessed by appearance of and cross-sectional measurement of the lumen in the ductal structures. Forskolin, cholera toxin and dbcAMP stimulated fluid transport and expansion in ductal structures over a 30 min, 2h and 2h period, respectively. Glucagon produced a similar response in 5 min, but the response was transitory, being almost complete reversed within 30 min. Secretin and vasoactive intestinal peptide produced a sustained response with maximal lumen expansion in 5-10 min. Somatostatin and gastrin caused marked reduction or disappearance of ductal lumens in 30 min, but was ineffective in reversing secretin induced duct distension. Application of the adrenergic agonists, epinephrine, isoproterenol, and phenylephrine resulted in the complete shrinkage of ductal lumens in 20-30 min. The ductules were also pH responsive, contracting at pH 7.0-7.2 and expanding at pH 7.8-8.0. PICM-19 bile duct cultures were positive for cytokeratin 7, aquaporin-1, and aquaporin-9 by Western blot analysis. Transmission electron microscopy analysis revealed that PICM-19 cells possessed single cilia. Results indicated cultured ductal structures of PICM-19 cells are a useful in vitro model for biliary epithelium.